A premium, widely-used utility that frequently releases updates for Samsung, Oppo, and Xiaomi Qualcomm devices.
Your phone has a locked SBL (Secondary Boot Loader). You need a "degraded" engineering bootloader. Search for eng_boot.img for your exact model. Flash it via fastboot ( fastboot flash boot eng_boot.img ), then retry the unlock tool.
The process often involves:
A V Techno Soft India Private Limited
Plot No. 116-B , Kh No. 8/7/2 Kotla Vihar 2 , Tilang Kotla , Nangloi
New Delhi - Delhi (India.) - 110041